The present invention relates to a composition suitable as an undercoat layer for paper coated with a thermosensitive recording layer.
The use of undercoats for thermosensitive recording materials is known to prevent undesirable absorption of ink into the paper and to provide thermal insulation for the paper. Consequently, coated paper produces sharper brighter images and has better reflectivity than uncoated paper.
U.S. Pat. No. 6,531,183 discloses a coating composition comprising binder and hollow pigment particles for improving gloss in paper. The coating composition may optionally comprise second pigment particles that may be solid or “vacuolated” and may be the same or different size as the first particles.
U.S. Pat. No. 6,780,820, discloses a variety of undercoats including those containing, inorganic pigments used in above critical pigment volume concentration coatings, fine organic single voided particles, or multivoided particles.
U.S. Pat. No. 8,334,047 discloses the use of an undercoat derived from a composition comprising a binder and a bimodal distribution of first and second hollow polymeric pigments with acid-free hydrophilic cores and with volume mean diameters generally in the range of 300 to 1,100 nm.
It would be an advance in the art of undercoating composition technology to find a material suitable for use as an undercoat that provides a balance of strength of the paper coating and the optical density of the printed paper coated with the undercoat and a thermo sensitive recording layer.